Energy Sources

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Notes

Energy from the Sun

The Sun transfers energy to Earth by **electromagnetic radiation** (mostly visible light and infrared).
Most energy resources on Earth come indirectly from the Sun: wind, waves, rain (hydroelectric), and plant growth (biofuels and fossil fuels).
Resources **not** from the Sun: **geothermal** (Earth's core heat), **nuclear** (elements in Earth's crust), **tidal** (mainly Moon's gravity).
**Solar cells** (photovoltaic) convert sunlight directly into electricity using semiconducting materials.
**Solar panels** use sunlight to heat water for domestic use; **solar furnaces** focus sunlight to boil water for steam turbines.
Advantages of solar: renewable, no pollution, reliable in sunny regions, can be used in remote areas, low running costs.
Disadvantages: low energy density (large area needed), intermittent, expensive to install, low efficiency (20–40%).

Wind Energy

Wind turns **turbines** → **generator** → electricity; energy transfers: kinetic (wind) → kinetic (turbine) → kinetic (generator) → electrical.
Advantages: renewable, no pollution, relatively cheap, high efficiency (~50%), land can still be used for farming.
Disadvantages: unreliable (wind not constant), visual pollution, each turbine produces little power, needs high-voltage lines.

Energy from Fuels: Fossil Fuels

Fossil fuels: **coal**, **natural gas** (methane), **crude oil** (refined into petrol, diesel). Formed from remains of plants/animals; chemical energy originally from sunlight via photosynthesis.
Advantages: reliable, responsive (can be turned on/off), well-established infrastructure, safe to store.
Disadvantages: **non-renewable** (millions of years to form, predicted to run out in ~200 years), burning releases **CO₂** (greenhouse gas) and **SO₂** (acid rain), extraction damages environment, expensive to build/decommission.
Uses: transport, electricity generation (burned to heat water → steam → turbine → generator), heating.

Energy from Fuels: Biofuels

Biofuels (ethanol, methane) made from plant matter; energy from sunlight stored chemically.
Advantages: **renewable**, considered **carbon neutral** (plants absorb CO₂ during growth), no SO₂ produced.
Disadvantages: requires land and resources for crops, only half the energy density of fossil fuels, controversial carbon neutrality (land could have been used for food).

Energy from Fuels: Nuclear Fuel

**Nuclear fission** splits large nuclei (e.g., uranium) into smaller ones, releasing energy; used to heat water → steam → turbine → generator.
Advantages: no atmospheric pollution, reliable, responsive, massive power output (twice that of fossil fuel plant), high energy density.
Disadvantages: **non-renewable** (finite uranium), produces **radioactive waste** (stored for thousands of years), expensive to build and decommission, risk of accidents.

Energy from Water

**Wave power**: underwater turbines turned by wave motion; **tidal power**: tidal barrages store water at height, released through turbines.
Advantages: renewable, no pollution, no fuel costs, tidal is reliable and predictable, high efficiency (~80%), responsive.
Disadvantages: few suitable locations (estuaries), interferes with shipping and habitats, technology not yet large-scale, wave power unreliable.
**Hydroelectric dams**: water stored in reservoir has gravitational potential energy; flowing water turns turbines.
Advantages: reliable, responsive, cheap to run, large electricity output, renewable.
Disadvantages: flooding valleys destroys habitats and settlements, expensive to build, drought can affect supply.

Geothermal Energy

Heat from Earth's core heats rocks; water injected into shafts is heated and returned as steam/hot water to generate electricity or heat homes.
Advantages: **renewable**, reliable (rocks hot for thousands of years).
Disadvantages: few suitable locations (tectonic activity), can release methane (greenhouse gas), expensive to build, small scale, low efficiency (~12%).

Nuclear Fusion (Extended Tier Only)

**Nuclear fusion** fuses hydrogen nuclei into helium, releasing massive energy (powers the Sun).
Requires extremely high temperatures and pressures; currently research aims to sustain fusion at lower temperatures.
Potential: virtually limitless, carbon-free electricity; but currently reactions require nearly as much energy as they release.

Particle arrangement in solids, liquids, and gases – relevant to energy transfer and fuel combustion.

Practice questions

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1.Which energy resource does not use the Sun as the source of its energy?
Easy
- AHydroelectric
- BWind
- CNuclear
- DCoal
2.Which energy resource involves splitting heavy nuclei?
Easy
- ANuclear fission
- BGeothermal
- CBiomass
- DNuclear fusion
3.Which energy resource does not release greenhouse gases?
Easy
- AOil
- BHydro-electric power
- CBiofuel
- DCoal
4.Which disadvantage does not apply to geothermal energy?
Easy
- AExpensive to build
- BFew suitable locations
- CCan result in the release of greenhouse gases
- DNot reliable
5.Which energy source relies on radiation from the Sun?
Easy
- AFossil fuels
- BNuclear fission
- CTidal power
- DGeothermal energy
6.Which source of energy is renewable?
Easy
- Acoal
- Bnatural gas
- Coil
- Dwind
7.Which energy resource does not originate from the Sun's radiation?
Easy
- Atidal power
- Bwind power
- Cwave power
- Dhydroelectric power
8.Listed below are some energy resources. W wind powering a turbine X water falling through a hydroelectric turbine Y alcohol made from crops which have been grown for burning in a biomass generator Z uranium for nuclear fission reactors Which of the resources are renewable?
Medium
- AW, X and Z
- BW and X
- CW, X and Y
- DW, X, Y and Z

More questions

9.Which statement best describes nuclear fuel as an energy source?
Medium
- AReliable & renewable
- BReliable, non-renewable and available for large scale production
- CUnreliable, non-renewable and available for large scale production
- DUnreliable, renewable & not available for large scale production
10.Which statement best describes the differences between solar cells and solar panels?
Medium
- ASolar cells use energy from the sun to heat water and solar panels use energy from the sun to generate electricity
- BSolar panels use energy from the sun to heat water and solar cells use energy from the sun to generate electricity
- CSolar cells use the kinetic energy of wind to produce electrical power and solar panels use energy from the sun to heat water
- DSolar panels use energy from the sun to produce electrical power and solar cells store the excess energy
11.What feature do geothermal, hydroelectric and nuclear energy sources share?
Medium
- ARenewable
- BCan generate large-scale energy
- CCause rotation in a generator
- DUse steam to turn a turbine
12.Which statement about nuclear fuel is correct?
Medium
- ANuclear waste must be stored for decades
- BNuclear fusion uses steam to turn a turbine which rotates a generator on a large scale
- CNuclear fission provides approximately 70% of the UK's energy
- DNuclear waste must be stored for thousands of years
13.A hydroelectric power station has a reservoir of water at a height of 50 m above the turbines. The water flows down and turns the turbines. Which energy transfer takes place as the water falls?
Medium
- Achemical to kinetic
- Bgravitational potential to kinetic
- Cnuclear to thermal
- Dkinetic to electrical
14.The efficiency of a solar cell is 20%. If 500 J of solar energy fall on the cell, how much electrical energy is produced?
Medium
- A100 J
- B400 J
- C500 J
- D2500 J
15.The graph shows the energy output of a solar cell and a wind turbine over 24 hours. The solar cell produces no energy between 18:00 and 06:00. The wind turbine produces a steady output of 2 kW from 00:00 to 12:00, then drops to 0.5 kW from 12:00 to 24:00. What is the total energy generated by the wind turbine in 24 hours?
Hard
- A30 kWh
- B60 kWh
- C48 kWh
- D24 kWh
16.Which energy resource uses the kinetic energy of moving air to generate electricity?
Easy
- Asolar power
- Bwind power
- Ctidal power
- Dgeothermal power
17.A student investigates the efficiency of a model wind turbine. The turbine is placed in a wind tunnel. The electrical power output is measured for different wind speeds. The results are shown in the table. Wind speed (m/s) | Power output (W) 2.0 | 0.5 4.0 | 4.0 6.0 | 13.5 8.0 | 32.0 Which conclusion is supported by the data?
Hard
- APower output is proportional to wind speed.
- BPower output is proportional to the square of wind speed.
- CPower output is proportional to the cube of wind speed.
- DPower output is inversely proportional to wind speed.
18.Which of the following is an advantage of using nuclear fission to generate electricity?
Medium
- AIt produces no radioactive waste.
- BIt uses a renewable fuel.
- CIt releases no greenhouse gases during operation.
- DIt can be built in any location.
19.A geothermal power station has an efficiency of 12%. It extracts 50 MW of thermal energy from hot rocks. What is the electrical power output?
Hard
- A6 MW
- B12 MW
- C44 MW
- D50 MW
20.A tidal barrage generates electricity by allowing water to flow through turbines as the tide goes out. Which statement about tidal power is correct?
Medium
- AIt is a non-renewable energy resource.
- BIt relies on the gravitational pull of the Moon.
- CIt produces atmospheric pollution.
- DIt is unreliable because tides are unpredictable.
21.A solar panel is used to heat water. Which statement explains how a solar panel works?
Medium
- AIt uses sunlight to generate electricity, which then heats the water.
- BIt absorbs infrared radiation from the Sun and transfers energy to the water.
- CIt reflects sunlight onto the water to heat it directly.
- DIt uses the kinetic energy of wind to pump water through a heater.
22.A student sets up the circuit shown to investigate how the power output of a solar cell depends on the angle of sunlight. The solar cell is connected to a variable resistor and an ammeter. The voltage across the cell is measured with a voltmeter. The angle of the light is changed and the current and voltage are recorded. Which row shows the correct units for the quantities measured?
Hard
- ACurrent in amperes, voltage in volts, power in watts
- BCurrent in volts, voltage in amperes, power in joules
- CCurrent in amperes, voltage in watts, power in volts
- DCurrent in watts, voltage in volts, power in amperes
23.Which energy resource is formed from the remains of ancient plants and animals?
Easy
- Anuclear fuel
- Bfossil fuels
- Cgeothermal energy
- Dsolar energy
24.A country has a coastline with strong tides and high rainfall. It also has volcanic regions with hot rocks underground. Which combination of energy resources would be most suitable for this country?
Medium
- Atidal power and geothermal energy
- Bsolar power and wind power
- Chydroelectric power and nuclear power
- Dwave power and fossil fuels
25.A student investigates the efficiency of a solar cell by measuring the electrical power output for different angles of sunlight. The solar cell is connected to a variable resistor and an ammeter. Which additional piece of equipment is needed to determine the electrical power output?
Medium
- AA voltmeter connected in parallel with the solar cell
- BA voltmeter connected in series with the solar cell
- CA light meter to measure the intensity of sunlight
- DA thermometer to measure the temperature of the solar cell
26.In a hydroelectric power station, water falls from a height of 50 m through a pipe to a turbine. The mass flow rate of water is 2000 kg/s. The gravitational field strength is 10 N/kg. Assuming no energy losses, what is the power output of the turbine?
Hard
- A1,000,000 W
- B100,000 W
- C10,000 W
- D1,000 W
27.A student sets up a model wind turbine in a wind tunnel and measures the electrical power output for different wind speeds. The results are shown in the table. Which graph best represents the relationship between power output and wind speed?
Medium
- AA curve that increases steeply as wind speed increases
- BA straight line through the origin
- CA horizontal line
- DA curve that increases then levels off
28.Which of the following energy resources relies on the gravitational pull of the Moon?
Easy
- ATidal power
- BWave power
- CHydroelectric power
- DWind power
29.A solar panel is used to heat water. Which statement best describes the energy transfer that occurs?
Medium
- ASolar energy is transferred to the thermal energy store of the water by radiation
- BSolar energy is transferred to the thermal energy store of the water by convection
- CSolar energy is transferred to the kinetic energy store of the water by conduction
- DSolar energy is transferred to the chemical energy store of the water by radiation
30.Which of the following is a renewable energy resource?
Easy
- ANatural gas
- BUranium
- COil
- DBiomass
31.A student investigates how the angle of sunlight affects the power output of a solar cell. The solar cell is placed at different angles to the light source, and the current and voltage are measured. Which variable should be kept constant to ensure a fair test?
Medium
- AThe distance between the light source and the solar cell
- BThe angle of the solar cell
- CThe current through the solar cell
- DThe voltage across the solar cell
32.The graph shows the energy output of a solar cell and a wind turbine over 24 hours. The solar cell produces no energy between 18:00 and 06:00. The wind turbine produces energy at all times but varies. Which statement is correct?
Hard
- AThe wind turbine is more reliable than the solar cell over 24 hours
- BThe solar cell is more reliable than the wind turbine over 24 hours
- CBoth are equally reliable
- DNeither is reliable at any time
33.Which of the following is a disadvantage of using nuclear fission to generate electricity?
Medium
- AIt produces radioactive waste that must be stored for thousands of years
- BIt releases large amounts of carbon dioxide into the atmosphere
- CIt is an unreliable energy source
- DIt is a renewable energy source
34.Which of the following is a non-renewable energy resource?
Easy
- ASolar
- BWind
- CNatural gas
- DHydroelectric
35.Which energy resource relies on the gravitational pull of the Moon?
Easy
- ATidal power
- BWave power
- CHydroelectric power
- DGeothermal power
36.Which of the following energy sources produce no atmospheric pollution?
Hard
- ANuclear fuel, wave power, and solar cells
- BFossil fuels, biofuels, and nuclear fuel
- CBiofuel, nuclear fuel, and wave power
- DWave power, solar cells, and geothermal power
37.A hydroelectric power station has a reservoir of water at a height of 50 m above the turbines. The water flows down and turns the turbines. Which energy transfer takes place in the water as it falls?
Medium
- Agravitational potential energy to kinetic energy
- Bkinetic energy to gravitational potential energy
- Cgravitational potential energy to electrical energy
- Dkinetic energy to electrical energy
38.A student investigates the efficiency of a model wind turbine. The turbine is placed in a wind tunnel. The electrical power output is measured for different wind speeds. The results are shown. At which wind speed is the turbine most efficient? (Efficiency = useful power output / power input × 100%)
Hard
- A5 m/s
- B10 m/s
- C15 m/s
- D20 m/s
39.A student sets up the circuit shown to investigate how the power output of a solar cell depends on the angle of sunlight. The solar cell is connected to a variable resistor and an ammeter. Which change would increase the power output of the solar cell?
Hard
- ADecreasing the resistance of the variable resistor
- BIncreasing the angle of incidence of sunlight (making it more oblique)
- CPlacing the solar cell in a shaded area
- DUsing a longer connecting wire
40.A student investigates how the power output of a solar cell depends on the angle of sunlight. The solar cell is connected to a variable resistor and an ammeter. The student adjusts the resistor to keep the current constant, and measures the voltage for different angles. Which of the following should be kept constant to ensure a fair test?
Medium
- AThe distance from the light source to the solar cell
- BThe resistance of the variable resistor
- CThe current through the circuit
- DThe voltage across the solar cell

Slides

Energy Sources Overview

Most energy resources on Earth come indirectly from the Sun.
The Sun heats the atmosphere, creating wind and waves; it evaporates water for rain; plants use sunlight for growth.
Some resources do NOT come from the Sun: geothermal (Earth's core heat), nuclear (elements in Earth's crust), and tidal (mainly Moon's gravity).
Renewable resources can be replenished at the same rate as they are used; non-renewable resources have a finite supply.

Which energy resource does NOT use the Sun as the source of its energy?

Hydroelectric
Wind
Nuclear
Coal

Energy from the Sun: Solar Cells & Panels

Solar cells (photovoltaic) convert sunlight directly into electricity using semiconducting materials.
Solar panels use sunlight to heat water for domestic use.
Solar energy is renewable and produces no pollution, but has low energy density and is intermittent.
Solar cells are around 20-40% efficient; solar panels can reduce energy bills.

Which of these are true about solar cells?

They generate electricity from sunlight.
They are made of semiconducting materials.
They are 100% efficient.
They can be used in remote locations.

Wind Energy

Wind turns turbines, which turn generators to produce electricity.
Wind is renewable, produces no pollution, and turbines have about 50% efficiency.
Disadvantages: unreliable (wind not constant), visual pollution, each turbine produces little power.

Which statement about wind power is correct?

It is a non-renewable resource.
It produces greenhouse gases.
It is reliable because wind always blows.
It uses kinetic energy of wind to generate electricity.

Fossil Fuels

Fossil fuels (coal, oil, natural gas) are formed from remains of plants and animals over millions of years.
They are non-renewable and release CO₂ and SO₂ when burned, causing pollution and acid rain.
Advantages: reliable, responsive, well-established infrastructure.

Fossil fuels are considered ____ because they take millions of years to form. Burning them releases ____ which contributes to the greenhouse effect.

Biofuels

Biofuels are made from plant matter (e.g., ethanol, methane).
They are renewable and considered carbon neutral, but this is controversial.
Disadvantages: require land and resources for crops, have half the energy density of fossil fuels.

Why is the claim that biofuels are carbon neutral controversial?

Because they release more CO₂ than fossil fuels.
Because the land could have been used for food crops, which would absorb CO₂ without releasing it when burned.
Because they are not renewable.
Because they produce sulphur dioxide.

Nuclear Fission

Nuclear fission splits large nuclei (e.g., uranium) into smaller ones, releasing energy.
Used in power stations to heat water, produce steam, turn turbines, and generate electricity.
Advantages: no atmospheric pollution, high energy density, reliable.
Disadvantages: non-renewable, radioactive waste must be stored for thousands of years, expensive to build and decommission.

Which of these are disadvantages of nuclear power?

It produces radioactive waste.
It releases greenhouse gases.
It is non-renewable.
Power stations are cheap to build.

Energy from Water: Hydroelectric, Wave & Tidal

Hydroelectric dams use gravitational potential energy of stored water to turn turbines.
Wave and tidal power use kinetic energy of water to generate electricity.
All are renewable and produce no pollution, but can damage habitats and are location-dependent.

A hydroelectric power station stores water in a reservoir. What type of energy does the water have in the reservoir?

Chemical
Kinetic
Gravitational potential
Nuclear

Geothermal Energy

Geothermal energy comes from heat in the Earth's core, accessed by drilling shafts and injecting water.
Hot water or steam can be used to generate electricity or heat homes.
Renewable and reliable, but limited to tectonically active areas, expensive, and can release methane.

Geothermal energy is obtained from ____ rocks below the ground. It is a ____ energy resource.

Nuclear Fusion (Extended Tier)

Nuclear fusion fuses small nuclei (e.g., hydrogen) into larger ones (e.g., helium), releasing massive energy.
It powers the Sun and could provide virtually limitless, carbon-free energy.
Currently, fusion requires extremely high temperatures and pressures; research aims to achieve net energy gain.

Which process releases energy in the Sun?

Nuclear fission
Nuclear fusion
Chemical combustion
Geothermal heating

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